1. Field of the Invention
The invention relates to packet traffic arbitration, and in particular, to a quota-based traffic management method for a device comprising both WLAN and Bluetooth modules.
2. Description of the Related Art
Typically, when multiple stations operating with different protocols share one common communication channel such as wireless radio frequency bands or wired cable connections, additional procedure is required to arbitrate packet traffics among the stations. WLAN and Bluetooth modules within a common system are taken as an example and explained in the following.
Referring to FIG. 1, a conventional wireless device 100 comprising both WLAN module 110 and Bluetooth module 120 is shown. According to predefined standards, WLAN module 110 and Bluetooth module 120 both operate at the same frequency band 2.4 GHz, and consequently, physical interferences are induced therebetween. Conventionally, IEEE 802.15.2 Packet Traffic Arbitration (PTA) is utilized to mitigate the physical interferences, whereby the WLAN module 110 and Bluetooth module 120 are activated exclusively in time domain. The PTA mechanism is basically a priority based control system. In FIG. 1, an arbitration circuit 130 is coupled to the WLAN module 110 and Bluetooth module 120, receiving request #RQ therefrom, and enabling either of them to perform RF activity such as medium access based on priorities of the request #RQ. A medium access operation may comprise either data transmission or data reception, or both.
Referring to FIG. 2a, a priority table 200 defining priorities of different traffic types is shown. In practice, traffic types are typically categorized into three types, Bluetooth (BT) synchronous connection oriented (SCO), BT asynchronous connectionless (ACL) and IEEE 802.11 WLAN traffics. IEEE 802.11 WLAN has the modest priority, while BT SCO traffic has the highest priority and BT ACL traffic lowest. It is noted that the priority table 200 is merely an example and designers can define priorities with respect to different traffics types for a system with coexisting WLAN and Bluetooth modules according to design necessity. When a request #RQ of a higher priority is issued from one module, traffic of a lower priority for the other module will be instantly suspended, and an exemplary flowchart is shown in FIG. 2b. 
Referring to FIG. 2b, a flowchart showing conventional priority control according to FIG. 2a is shown. In step 201, a request #RQ from either WLAN module 110 or Bluetooth module 120 is issued, and its priority is looked up in the priority table 200. In step 203, the arbitration circuit 130 may check whether any traffic of higher priority is currently active on the opposing module. For example, if the request #RQ is issued from the WLAN module 110, the Bluetooth module 120 is checked, and vice versa. If a positive result is checked in step 203, the current request #RQ is rejected in step 209. Otherwise, if all other traffics of higher priorities are inactive on the opposing module, the request #RQ is granted, and the process goes to step 205. In step 205, traffic of lower priorities on the opposing module is unconditionally suspended. For example, when a request #RQ of IEEE 802.11 is issued from the WLAN module 110, the Bluetooth module 120 is checked whether a BT SCO traffic is active. The request #RQ of IEEE 802.11 is only granted when the BT SCO traffic is inactive, and when it is granted, any traffic of lower priority such as BT ACL on the Bluetooth module 120 will be forcibly suspended, allowing the traffic of IEEE 802.11 to be activated. In step 207, only when the traffic of lower priorities on the opposing module is suspended, the traffic corresponding to the granted request #RQ is initiated by sending an enable signal #EN to the module where the request #RQ is originated from. Steps 207 and 209 are followed by step 211, concluding the flowchart.
Summarizing, a request #RQ of the highest priority, such as BT SCO, will be unconditionally granted to interrupt RF activities of IEEE 802.11. On the other hand, a request #RQ of the lowest priority, such as BT ACL, is only granted when the traffic of IEEE 802.11 is inactive, and always vulnerable to interruptions from higher priority request #RQ when accessing medium. In other words, traffic of lower priority may not be efficiently accomplished when traffic of higher priority is existing, and the process of unconditionally suspending a requested medium access may significantly increase medium access failure. It is therefore desirable to provide an enhanced control approach to arbitrate traffics of multiple stations sharing a common channel.